The present invention relates generally to apparatus for horizontal stacking of sheets or signatures received from a web press, and more particularly to a novel method and apparatus for horizontal stacking of sheets in a manner providing improved support of the stacked sheets and enabling precise batches of sheets to be readily removed by an operator from the horizontal stack.
It is a common practice in the art of web press printing to convey successive sheets or signatures downstream from the web press in a generally flat partially overlapped or shingled orientation. The successive sheets are initially conveyed along a generally horizontal path during which they may pass between crusher rolls for removing air from between the overlapped sheets, followed by passage through a jogger station operative to jog the sheets into precise overlying relation. The successive conveyed sheets are then stacked in either a generally vertical stack from which bundles or batches of sheets are removed, or in a horizontal stack preparatory to removing batches of sheets.
Vertical stack forming systems exhibit significant drawbacks in that the stack height is limited and the weight of the stack can cause sheet backups if not promptly removed. The known vertical sheet stacking systems also mark the stack at a particular height to define each successive bundle of sheets. This marking technique makes it difficult for an operator to accurately separate and readily remove bundles of predetermined sheets from the stack.
In another prior vertical sheet stacking system, successive sheets or signatures are conveyed flat along a horizontal path and deposited onto a vertical stack supported on a downstream conveyor until a stack of a predetermined number of sheets is formed. The upstream conveyor must then be interrupted while the downstream conveyor is moved or indexed to present a new stack position for receiving sheets from the upstream conveyor. This system significantly reduces the speed at which vertical of stacks sheets may be formed.
In prior horizontal sheet stacking systems, successive sheets or signatures from the web press pass from a generally horizontal conveyor path through a loop conveyor section operative to convey the sheets in an upward generally vertical direction so that the leading edge of each successive sheet engages a stop after which the sheets undergo horizontal movement into a horizontal stack while remaining generally vertically disposed.
A significant drawback in the known horizontal sheet stackers is that they fail to provide a suitable demarcation between each predetermined number of vertically oriented sheets that constitute a desired batch and the sheets immediately following that will comprise the next successive batch of sheets. As a result, it is difficult for an operator to rapidly and accurately remove each successive batch of sheets from the horizontal stack.
Other known horizontal sheet stackers attempt to identify each successive batch of vertically disposed sheets by placing a visual marking on the upper edge of either the last sheet in each batch or the first sheet in the next successive batch. However, the marker generally marks the upper edges of a plurality of adjacent sheets so that an accurate identification of the exact trailing end sheet of each batch of sheets cannot be made. Moreover, the marking is frequently difficult to see, thus further inhibiting removal from the horizontal stack of a precise number or batch of sheets.
Still another drawback in the known horizontal sheet stackers is that when successive sheets conveyed upwardly by the loop conveyor engage a stop and are moved horizontally to form a horizontal stack, the sheets are only supported at their lower transverse edges and at their forward and rearward planar surfaces. The vertically disposed sheets may therefore move laterally in the planes of the sheets. Such movement causes the vertical sheet edges that were previously aligned by the jogger to become misaligned, thereby preventing the formation of coplanar side edge surfaces on each batch of sheets. There thus exists a need for a horizontal sheet stacker and batcher that overcomes the drawbacks in prior horizontal sheet stackers and enables precise and rapid removal of batches of sheets while operating at high production rates.
A general object of the present invention is to provide a method and apparatus for horizontal stacking and batching of sheets or signatures received from a web press wherein significantly improved efficiency and accuracy is achieved at relatively high operating speeds.
A more particular object of the present invention is to provide a method and apparatus for horizontal stacking and batching of generally rectangular sheets or signatures received in shingled relation from a web press wherein successive sheets are conveyed upwardly from a generally horizontal path to a stop mechanism operative to create a physical demarcation between each successive predetermined batch of horizontally stacked sheets, thereby enabling an operator to quickly and accurately remove a predetermined batch of sheets from the horizontal stack.
Another object of the present invention is to provide a horizontal sheet stacking and batching system operative to convey successive shingled generally rectangular sheets or signatures from a web press to a batch forming trough in which the vertically disposed sheets are supported at two downwardly facing edges and at their forward and rearward generally planar surfaces so that aligned lateral edges of the sheets remain coplanar as the sheets move along the trough and when a batch of sheets is removed from the trough.
Another object of the present invention is to provide a method and apparatus for conveying generally rectangular sheets or signatures in shingled relation downstream from a web press wherein successive sheets are rotated about their paths of travel from generally flat horizontal positions to positions inclined to horizontal as they travel along a progressively inclined conveyor section after which the sheets are conveyed in an upward direction along a path normal to the leading edges of the sheets as they leave the downstream end of the inclined conveyor section, thereby orienting the sheets to establish two downwardly facing edges for supporting the sheets as they enter a generally V-shaped trough to form a horizontal stack.
Another object of the present invention is to provide accessories cooperative with the sheet receiving trough of the sheet stacker/batcher that facilitate placement of batches of sheets into a container box or the like, or in position for transfer onto a pallet or to a banding apparatus.
A feature of the present invention lies in the provision of an oscillator roller operatively associated with the conveyor belts forming the upper reach of the conveyor section that inclines the sheets from a horizontal orientation to an inclined orientation as the sheets are conveyed from an upstream end to a downstream end of the inclined conveyor section. The oscillator roller causes the conveyor belts to undergo oscillating or vibrating movement and thereby assist in lateral downward movement of the sheets against an edge guide as they travel along the inclined conveyor path, thus eliminating the need for a jogging mechanism.
Another feature of the present invention lies in positioning an upstream conveyor section so as to be angularly inclined in a generally horizontal plane relative to the direction of sheet travel from the web press so that successive rectangular shingled sheets or signatures passing to the downstream conveyor section have at least one corner individually exposed to facilitate optical counting of the sheets being conveyed downstream.
Still another feature of the present invention lies in providing an edge guide that extends substantially the length of the inclined conveyor section and defines a stop engaged by the lower longitudinal edges of the inclined sheets traversing the inclined conveyor path, the edge guide eliminating the need for a jogger mechanism and being configured to prevent the sheets from inadvertent release from the corresponding conveyor belts.
Another feature of the horizontal sheet stacking and batching apparatus in accordance with the invention lies in providing conveyor belts along each of two upwardly facing surfaces of the V-shaped trough to engage downwardly facing edges of the vertically oriented sheets entering the trough and assist in movement of the sheets along the trough. Backstop plates moveable along the length of the trough enable an operator to isolate successive batches of sheets for removal from the trough.
Further objects, features and advantages of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings wherein like reference numerals designate like elements throughout the several views.